Hickory Grove Lake IA 03-SSK-950

Story County S24T83NR22W 2.5 mi SW of Colo.

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

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Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Stable
Created: 12/27/2021 10:20:35 AM
Updated: 1/5/2022 10:43:36 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Moderate

Status

Delisted

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Cycle Delisted

2022

Delisting Rationale

TMDL preparation and approval

Data Source

TMDL monitoring: Iowa DNR

Turbidity: Secchi Disk Transparency

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

New

Source

Agriculture

Source Confidence

Low

Cycle Added

2022

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier I

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class HH

Human Health -

Fully Supported

Impairment Delistings

Cycle Added	Class	Cause	Data Source	Rationale
2016	Class A1	Algal Growth: Chlorophyll a	Ambient monitoring: Iowa DNR-lakes	New data: WQ improvement (chemical / physical / bacterial)

Documentation

Assessment Summary

The Class A1 use was assessed as “not supported” due to levels of indicator bacteria that exceeded Iowa’s water quality standard and aesthetically objectionable conditions caused by non-algal turbidity. The Class BLW use was assessed (monitored) as “fully supported.” The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data. Note: A TMDL for indicator bacteria E. coli at Hickory Grove Lake was prepared by DNR and approved by EPA in June 2020. Because not all of the section 303(d) impairments identified for the current assessment/listing cycle (Turbidity) are addressed in the TMDL. This waterbody remains in Category 5a (impaired; TMDL required) for the current assessment/listing cycle.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2016-2018	22850001	Hickory Grove Lake (maximum water depth)
Iowa DNR	6	FT	See Below	302	Hickory Grove Lake	Hickory Grove Park

Class A1 - Indicator Bacteria: No Data. See previous assessments.

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
22850001	6	9 / 3	7.4	8.7	8.2	0	3	NO	Evaluated	Full

Class A1 - Lake TSI's:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median TSI Violation?	Assessment Type	Support Level
22850001	6	Chlorophyll a TSI	9 / 3	36	66	58	NO	Monitored	Full
22850001	6	Secchi TSI	9 / 3	40	70	65	YES	Monitored	Not
22850001	6	Total Phosphorus TSI	9 / 3	44	85	63	NA	NA	NA
22850001	6	Inorganic suspended solids	9 / 3	0.6	10	3	NA	NA	NA

DNR's assessment methodology indicates that at least two assessment/listing cycles with a TSI value less than or equal to 63 are necessary to suggest de-listing of an impairment. The chlorophyll a TSI value for the 2016 assessment listing cycle was 65, which based on DNR's assessment/listing methodology indicated an impairment based on the narrative criteria protecting against aesthetically objectionable conditions. Because the TSI value for the 2020 assessment/listing cycle was less than the trigger of 65 (2020 listing for chlorophyll a was 60), and because the TSI value for the current listing cycle is also 58, based on DNR's methodology, these values suggest "full support" of the Class A1 uses protecting against aesthetically objectionable conditions and the impairment (5a) for chlorophyll a is suggested for delisting for the 2022 assessment/listing cycle.

Class BLW - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
22850001	6	Ammonia	9 / 3	0.0003	0.135	0.06	NA	0 / 0	3	NO	Evaluated	Full
22850001	6	Dissolved Oxygen	9 / 3	3.6	11.6	9.3	1	NA / NA	3	NO	Evaluated	Full
22850001	6	pH	9 / 3	7.4	8.7	8.2	0	NA / NA	3	NO	Evaluated	Full
22850001	6	Temperature	9 / 3	19.8	28	23.6	0	NA / NA	3	NO	Evaluated	Full

Class BLW - Lake Planktonic Cyanobacteria:

Site ID	Data Source ID	# Samples	Maximum Cyanobacteria Wet Mass	Maximum Cyanobacteria % Composition	Median Cyanobacteria Wet Mass	Median Cyanobacteria % Composition	Median Cyanobacteria Concentration = 75th Percentile	Assessment Type	Support Level
22850001	6	5	54.47	95.8%	4.65	29.9%	NO	Evaluated	NA

Class HH - Fish Tissue Sampling:

Site ID	Biopart	Year	Species	# in sample / # of samples	Avg Length (cm)	(Avg) Hg (ppm)	Chlordane (ppm)	Sum PCBs (ppm)
302	fillet	2013	channel catfish	5	45	0.09	<0.2	<0.6
302	tissue plug	2013	largemouth bass	5	32.9	0.239
Support Level	Full

Monitoring and Methods

Assessment Key Dates

6/20/2016

Fixed Monitoring Start Date

9/11/2018

Fixed Monitoring End Date

8/2/2013

Fish Tissue Monitoring

9/16/2013

Fish Tissue Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

222

Non-fixed-station monitoring (conventional during key seasons and flows)

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring